1. Field of the Invention
This invention relates to the field of conduit obstruction removal, and in particular it relates to methods for removing obstructions from the interior of conduits.
2. Description of the Art
Fluid-handling conduits, including industrial, municipal, household, and agricultural process and water inlet and drain lines, as well as inline equipment such as orifices, nozzles, valves, screens, filters, metering devices, heat exchangers, etc., often become fouled or completed plugged with organic or inorganic debris, impurities, corrosion, and/or components of the fluid customarily passed through the conduit. A variety of physical and chemical procedures and compositions have been devised to dissolve or physically dislodge most if not all types of such organic and inorganic obstructions. For instance, it is known that acids, such as sulfuric acid, will dissolve a variety of inorganic obstructions such as metal salts, carbonates, and other materials and that they will chemically attack and weaken a variety of organic obstructions thereby facilitating the removal of such organic obstructions.
Sulfuric acid is one the strongest, readily available acids and, but for a number of significant disadvantages associated with use of sulfuric acid, it is an ideal candidate for the removal of obstructions from conduits. However, sulfuric acid is highly corrosive and therefore difficult to handle, and it can cause severe corrosive damage to conduits and in-line equipment. It promotes a variety of side reactions with many materials including dehydration, sulfonation, and oxidation, in which it is consumed, thereby eliminating its activity as an active chemical agent. Its heat of dilution in many solvents, particularly in water, is very high, and therefore the addition of sulfuric acid to water and other solvents must be handled with great care. In fact, these disadvantages are so severe that they eliminate sulfuric acid as a viable obstruction-removing agent in many circumstances.
Jones, in U.S. Pat. No. 4,116,664, disclosed that the addition of urea to sulfuric acid to form certain combinations of urea and sulfuric acid resulted in a product which was non-toxic, non-caustic, and non-corrosive to black iron and that, therefore, it could be safely transported, handled, stored, and applied, as a fertilizer, with ordinary equipment. Both Jones, supra, and Verdegaal et al. (U.S. Pat. No. 4,310,343) disclose methods for producing certain combinations of urea and sulfuric acid. Verdegaal et al. disclosed methods of manufacturing urea-sulfuric acid compositions which contain at least 50 weight percent urea.
Other authors have also discussed the nature and manufacture of combinations of urea and sulfuric acid. For instance, D. F. du Toit, Verslag Akad. Wetenschappen, 22, 573-4 (abstracted in chemical abstracts, 8, 2346, 1914) and L. H. Dalman, "Ternary Systems of Urea and Acid" JACS, 56, 549-53 (1934), disclosed that urea forms mono- and diurea adducts with sulfuric acid. Dalman defined the phase relationships between the solid phase and saturated solutions containing urea and sulfuric acid at certain temperatures. While these authors described several characteristics of and methods for manufacturing combinations of urea and sulfuric acid, they did not observe that certain urea-sulfuric acid compositions are particularly active protenating and hydrolyzing agents in which the disadvantages customarily associated with sulfuric acid, such as its dehydrating, sulfonating, and oxidizing activity, are markedly reduced.